Globals vs Const Globals vs Closures

bench.jl

a = 3
const b = 3

g(f::Function, N) = f(N)

function f_glob(N)
    s = 0
    for i = 1:N
        s += a
    end
    s
end

function f_const_glob(N)
    s = 0
    for i = 1:N
        s += b
    end
    s
end

function f_clos(N, c)
    function f_inner(N)
        s = 0
        for i = 1:N
            s += c
        end
        s
    end

    g(f_inner, N)
end

println("warmup...")
@time 1
f_glob(1)
f_const_glob(1)
f_clos(1, 3)

println("Non-const global")
gc(); @time f_glob(10^6)
println("Const global")
gc(); @time f_const_glob(10^6)
println("Closure")
gc(); @time f_clos(10^6, 3)

nothing